Treatment of stroke with bone marrow stromal cells (MSCs) significantly improves functional recovery in experimental stroke. However, little is known about temporal and spatial profiles of migration of transplanted MSCs and the effects of these cells on host cerebral tissue leading to functional recovery. We propose to develop noninvasive in vivo magnetic resonance (MR) methodology for tracking transplanted MSCs and investigating their effects on the host brain. In Specific Aim 1, we will first optimize methodology for magnetic contrast agent labeling and in vivo three dimensional magnetic resonance (MRI) monitoring of transplanted MSCs in the host brain. Using the optimized methodology, we will then examine the effects of different routes (intravenous vs intracisternal) of transplantation on survival, migration, and distribution patterns of transplanted cells in brain subjected to stroke. In Specific Aim 2, dynamic effects of transplanted MSCs on the host brain angiogenesis and functional recovery after stroke will be noninvasively measured by means of MR. Neurological outcome will be measured using a battery of behavioral tests. Correlation between changes in MR measurements and dynamic functional improvements will be analyzed in the same animal. In addition, changes in MR measurements of angiogenesis resulting from MSC transplantation will be verified using three dimensional laser scanning confocal microscopy in combination with immuno-histochemistry. With these novel approaches, we expect that noninvasive MR measurements will simultaneously detect the migration and distribution of transplanted cells and the effects of these cells on the host brain tissue, and that changes in MR measurements will correlate to neurological function. Therefore, MR could potentially provide important noninvasive measurements for developing a successful cell therapy for stroke. After completing our studies, we expect to demonstrate that MR tracking magnetic labeled cells is a valid new technique for studying cell therapy for stroke, which will lead to optimization of cell transplantation protocols and improved management of stroke.